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At least 127 records · Page 7

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DOE OSTI2025

Thermal shock resistance of lightweight cements developed for geothermal conditions

Cements are a critical component in well construction, as they act to prevent well fluid and gas escape, prevent corrosion of the casing, and strengthen the wellbore to prevent deformation. Under the high temperature/pressure conditions common in geothermal systems, the injection of cold water for energy production is expected to induce cyclic damage to the borehole cement through the rapid temperature fluctuations. These “thermal shocks” are expected to cause casing shrinkage, annulus formation, and cement tensile stresses. To understand the effect of cold water injection on the wellbore environment, a set of rock-cement-steel samples were created to simulate the structure of a geothermal well. Lightweight thermally-insulating cement blends were tested under thermal shock conditions in this study. In each test, the samples were pressurized to an effective pressure of ~3.5 MPa and placed at high temperatures. Thermal shocks were performed by injecting cold water (~10-15 °C) through the samples at a constant rate while keeping the samples at high temperatures until the sample temperature stopped decreasing and deformation ceased. Eight thermal shock tests were conducted with each sample – two at 100 °C and six at 200 °C. Post-tests analysis was then conducted by cutting open each sample to examine the damage in each component of the simulated wellbore. Experimental results suggest that all samples experienced similar degrees of axial and lateral contraction during cold water injection, but for the most part this contraction is recoverable when injection halts. Post-test analysis revealed that fly ash cenosphere pre-treatment had the best effect on improving thermal shock resistance in the cement blends. Thermomechanical modeling of likely stress paths experienced by the cements during heating/cooling cycles shows that elasto-plastic cement constitutive behavior results in most plastic strain occurring during the initial heating steps, with mostly elastic strain occurring during the thermal shock cycles. In conclusion, this agrees with experimental evidence, suggesting that cement damage from shocking occurs via other mechanisms such as chemical alteration, corrosion, and fatigue.

36 MATERIALS SCIENCE↗

DOE OSTI2020

BinaryCIF and CIFTools—Lightweight, efficient and extensible macromolecular data management

3D macromolecular structural data is growing ever more complex and plentiful in the wake of substantive advances in experimental and computational structure determination methods including macromolecular crystallography, cryo-electron microscopy, and integrative methods. Efficient means of working with 3D macromolecular structural data for archiving, analyses, and visualization are central to facilitating interoperability and reusability in compliance with the FAIR Principles. We address two challenges posed by growth in data size and complexity. First, data size is reduced by bespoke compression techniques. Second, complexity is managed through improved software tooling and fully leveraging available data dictionary schemas. To this end, we introduce BinaryCIF, a serialization of Crystallographic Information File (CIF) format files that maintains full compatibility to related data schemas, such as PDBx/mmCIF, while reducing file sizes by more than a factor of two versus gzip compressed CIF files. Moreover, for the largest structures, BinaryCIF provides even better compression—factor ten and four versus CIF files and gzipped CIF files, respectively. Herein, we describe CIFTools, a set of libraries in Java and TypeScript for generic and typed handling of CIF and BinaryCIF files. Together, BinaryCIF and CIFTools enable lightweight, efficient, and extensible handling of 3D macromolecular structural data.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Computational investigations of Dienes defect- and vacancy-induced changes in the electronic and vibrational properties of carbon fiber structural units

Carbon fiber (CF) is a promising lightweight alternative to steel and is of significant interest for energy applications. As CF continues to find new uses and is exposed to new external conditions, a noninvasive method of monitoring its structural integrity is critical. Raman spectroscopy is a commonly used method for this monitoring; however, it is highly inferential, and the interpretation of the data is not always straightforward. In this work, we perform density functional theory (DFT) calculations to investigate changes in the vibrational properties of CF structural units (i.e., graphene and graphite) caused by monovacancy and Dienes defects as a foundation for modeling more complex defects that move our model toward that of realistic CF. Using large computational supercells, we can understand how these defects change the electronic structure and vibrational properties of graphene and graphite for interdefect distances near those of the lower experimental limit. The monovacancy opens an electronic bandgap at the K point. Although no such electronic gap is opened by the Dienes defect, both defects introduce flat defect bands near the Fermi energy. The Dienes defect creates long-range deviations of the phonons, leading to substantial broadening of the highest frequency optical modes in the band structure compared to that of the pristine material. In contrast, the phonon changes caused by the monovacancy are short range, and only minor changes in the band structure or phonon density of states were observed. These findings can assist in the interpretation of experimental results by providing atomic-scale insight into key electronic and vibrational features.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

The Use of Additive Manufacturing for Fabrication of Multi-Function Small Satellite Structures

The use of small satellites in constellations is limited only by the growing functionality of smallsats themselves. Additive manufacturing provides exciting new design opportunities for development of multifunction CubeSat structures that integrate such functions as propulsion and thermal control into the satellite structures themselves. Manufacturing of these complex multifunction structures is now possible in lightweight, high strength, materials such as titanium by using existing electron beam melting additive manufacturing processes. However, the use of today's additive manufacturing capabilities is often cost-prohibitive for small companies due to the large capital investments required. To alleviate this impediment the U.S. Department of Energy has established a Manufacturing Demonstration Facility (MDF) at their Oak Ridge National Laboratory (ORNL) in Tennessee that provides industry access to a broad range of energy-efficient additive manufacturing equipment for collaborative use by both small and large organizations. This paper presents a notional CubeSat multifunction design that integrates the propulsion system into a three-unit (3U) CubeSat structure. The full-scale structure has been designed and fabricated at the ORNL MDF. The use of additive manufacturing for spacecraft fabrication is opening up many new possibilities in design and fabrication capabilities for what had previously been impossible structures to fabricate.

Horais, Brian J↗

DOE OSTI2026

Additively Reinforced Thermoformable PETG Composite Sheets for Improved Structural Efficiency

Thermoforming of short-fiber reinforced thermoplastic sheets offers a viable pathway for producing lightweight composite components; however, inherent anisotropy in fiber-reinforced sheets can limit structural performance under multidirectional loading. In this work, short carbon fiber, glass fiber, and hybrid fiber–reinforced PETG sheets were evaluated as candidate feedstock materials for thermoforming, with flexural and tensile testing performed both along the primary fiber direction and in the off-axis orientation to establish baseline stiffness, strength, and anisotropy. As expected, short carbon fiber PETG exhibited the highest stiffness and strength in the primary fiber direction, while all systems showed reduced performance in the off-axis direction. This off-axis performance reduction provides clear justification for the use of additive reinforcement when such thermoformed sheets are intended for structural applications. The intended manufacturing sequence involves thermoforming the reinforced sheet first, followed by the application of additively manufactured lattice reinforcement; therefore, the reinforcement strategy does not impose limitations on sheet formability during thermoforming. Post-forming lattice reinforcement significantly reduced load-normalized displacement by approximately 95–99% relative to non-reinforced sheets and improved weight-normalized stiffness by ~70%. These findings demonstrate that geometry-driven additive reinforcement can effectively compensate for off-axis property reductions in thermoformed PETG composites, enabling enhanced multidirectional structural performance without compromising manufacturability.

Talabi, Isaac [ORNL] (ORCID:0000000340215594)↗

DOE OSTI2020

Solving Eco-Driving Problems Using Indirect Collocation Method and Smooth Representation

Here, we discuss the eco-driving problem, considering both electric and conventional powertrains, and presents a pathway to solving it numerically using an indirect collocation method. Despite the low-order system dynamics, the piecewise fuel/efficiency map, gear shifting, and real-world traffic/road situations bring system discontinuities/switchings and pure state constraints into the problem formulation, which make the problem highly nonlinear and nontrivial to solve. This letter introduces smooth approximations to convert the original problem to an unconstrained (and penalized) smooth boundary-value problem. This approach eliminates the discussion of the switching structure and leads to a lightweight Newton-method-based solution procedure.

42 ENGINEERING↗

DOE OSTI2019

Advances in Dissimilar Metals Joining through Temperature Control of Friction Stir Welding

Lightweighting of vehicles and portable structures is an important undertaking. Multi-material design is required to achieve conflicting design targets such as cost, stiffness, and weight. Friction stir welding (FSW) variants, such as friction stir dovetailing and friction stir scribe, are enabling technologies for joining of dissimilar metals. This work shows that FSW variants are capable of joining aluminum to steel. Characteristics of metallurgical bonding at the dissimilar material interface are strongly affected by weld temperature. Control of FSW process temperature enables metallurgical bonding with suppressed formation of intermetallics at the dissimilar material interface resulting in improved mechanical properties relative to competing techniques. Temperature control is a powerful tool for process development and to ensure weld quality of dissimilar material welds.

Aluminum to Steel Joining, Friction stir welding, ↗

DOE OSTI2017

Nanoscale Structure–Property Relationships of Polyacrylonitrile/CNT Composites as a Function of Polymer Crystallinity and CNT Diameter

Polyacrylonitrile (PAN)/carbon nanotube (CNT) composites are used as precursors for ultrastrong and lightweight carbon fibers. However, insights into the structure at the nanoscale and the relationships to mechanical and thermal properties have remained difficult to obtain. In this study, molecular dynamics simulation with accurate potentials and available experimental data were used to describe the influence of different degrees of PAN preorientation and CNT diameter on the atomic-scale structure and properties of the composites. The inclusion of CNTs in the polymer matrix is favored for an intermediate degree of PAN orientation and small CNT diameter whereas high PAN crystallinity and larger CNT diameter disfavor CNT inclusion. The glass transition at the CNT/PAN interface involves the release of rotational degrees of freedom of the polymer backbone and increased mobility of the protruding nitrile side groups in contact with the carbon nanotubes. The glass-transition temperature of the composite increases in correlation with the amount of CNT/polymer interfacial area per unit volume, i.e., in the presence of CNTs, for higher CNT volume fraction, and inversely with CNT diameter. The increase in glass-transition temperature upon CNT addition is larger for PAN of lower crystallinity than for PAN of higher crystallinity. Interfacial shear strengths of the composites are higher for CNTs of smaller diameter and for PAN with preorientation, in correlation with more favorable CNT inclusion energies. The lowest interfacial shear strength was observed in amorphous PAN for the same CNT diameter. PAN with ~75% crystallinity exhibited hexagonal patterns of nitrile groups near and far from the CNT interface which could influence carbonization into regular graphitic structures. The results illustrate the feasibility of near-quantitative insights into macroscale properties of polymer/CNT composites from simulations of nanometer-scale composite domains. Guidance is most effective when key assumptions in experiment and simulation are closely aligned, such as exfoliation versus bundling of CNTs, size, type, potential defects of CNTs, and precise measures for polymer crystallinity.

Materials Science↗

DOE OSTI2013

Optimal design at inner core of the shaped pyramidal truss structure

Sandwich material is a type of composite material with lightweight, high strength, good dynamic properties and high bending stiffness-to-weight ratio. This can be found well such structures in the nature (for example, internal structure of bones, plants, etc.). New trend which prefers eco-friendly products and energy efficiency is emerging in industries recently. Demand for materials with high strength and light weight is also increasing. In line with these trends, researches about manufacturing methods of sandwich material have been actively conducted. In this study, a sandwich structure named as “Shaped Pyramidal Truss Structure” is proposed to improve mechanical strength and to apply a manufacturing process suitable for massive production. The new sandwich structure was designed to enhance compressive strength by changing the cross-sectional shape at the central portion of the core. As the next step, optimization of the shape was required. Optimization technique used here was the SZGA(Successive Zooming Genetic Algorithm), which is one of GA(Genetic Algorithm) methods gradually reducing the area of design variable. The objective function was defined as moment of inertia of the cross-sectional shape of the strut. The control points of cubic Bezier curve, which was assumed to be the shape of the cross section, were used as design variables. By using FEM simulation, it was found that the structure exhibited superior mechanical properties compared to the simple design of the prior art.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2025

X-ray and neutron diffraction patterns of the AlCrTiV high-entropy alloy and quaternary Heusler structures

The quaternary alloy AlCrTiV has been proposed as both a lightweight high-entropy alloy and also a functional spin filter material based on the Heusler structure. Experimental investigations to-date, based on X-ray diffraction, offer conflicting interpretations of the structure. Here we simulate diffraction patterns of the various proposed structures to show that neutron diffraction, in particular, can reveal the nature of long-range chemical order and discriminate among distributions of the refractory transition metals. Magnetic contributions to the neutron diffraction are also discussed.

Kalliney, Nedjma [Carnegie Mellon Univ., Pittsburg↗

DOE OSTI2019

Comparing non-destructive 3D X-ray computed tomography with destructive optical microscopy for microstructural characterization of fiber reinforced composites

Due to their lightweight, relatively high stiffness properties, and formability into complex shapes, discontinuous fiber composites are advantageous for producing small and medium size components. Improved characterization techniques and post-processing methodologies are required for more reliable quantification of the microstructure and defect distributions in these materials, in order to employ model-based approaches to assess their structural integrity. This work compares a non-destructive X-ray approach with a destructive optical microscopy approach for characterizing the microstructural attributes, specifically the fiber volume fraction, porosity volume fraction, fiber orientation distribution, and fiber length distribution of discontinuous glass fibers in a polypropylene matrix. Additionally, a method for destructively determining the ambiguous components of the orientation tensor (related to the sign ambiguity of the out-of-plane angle in a destructive cross-sectional cut of a fiber) over a large surface area is included. It was found that fiber volume fraction and average fiber aspect ratio matched well, while fiber orientation and porosity detection had small but notable differences. The differences in the detection capabilities of each technique are quantified and discussed shedding light on the specific advantages and disadvantages of each approach, and enabling engineers to quantify uncertainty in their microstructural characterization measurements especially as they relate to model based structural integrity activities.

Non-destructive testing↗

DOE OSTI2020

Abstract for CRADA between the National Energy Technology Laboratory and General Motors (AGMT-0876)

Lightweight aluminum shape castings have widespread applications for structural components in the automotive, aerospace, and general engineering industries because of their excellent castability, corrosion resistance, and particularly high strength-to-weight ratio in the heat-treated condition. In the automotive industry, cast aluminum alloys have been increasingly used to replace cast iron and steel in vehicle applications such as engine blocks, cylinder heads, intake manifolds, brackets, housings, chassis, transmission parts, and suspension systems to reduce mass. As many of the aluminum shape castings used in automobiles involve cyclic loading, fatigue properties of the castings are critical to their success. The increasing use of lightweight aluminum cast components in critical structures thus requires improved integrity, with more reliable and quantifiable performance. The objective of this project is to demonstrate and further develop GM’s patent-pending, novel casting process, “Pressure-Assistant Precision Sand Casting (PAPSC) for producing flawless cast aluminum cylinder heads with minimum manufacturing and energy costs”. The approach is to leverage NETL’s experience in producing high-quality metal castings through various microstructure control and defect elimination technologies as well as comprehensive quantification of microstructure characteristics and mechanical properties. A baseline (production) alloy together with the melt treatment will be initially evaluated with the new PAPSC process to develop and validate the process window for producing flawless cast aluminum heads.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Molecular Dynamics Simulation of Hygroscopic Aging Effects in Epoxy Polymer

The automobile industry is incorporating more lightweight content in car designs to boost fuel-economy. New structural adhesives are needed to mitigate the corrosion and thermal expansion issues associated with joining dissimilar lightweight materials, but adhesive developers lack a fundamental understanding of the chemistry that occurs in the adhesive as the joint ages. In this study, we developed structural adhesive molecular models and applied classical molecular dynamics simulations and density functional theory calculations to gain molecular insights into the influence of water molecules on the properties of epoxy-based adhesives (DGEBA + Jeffamine (JD230)). The simulations were complemented by experimental synthesis and characterization. Our work underscores the impact of water molecules on the local structure of the epoxy network as well as resulting mechanical properties. Water molecules were mainly coordinated with hydroxyls, primary amines and secondary amines, but also weakly coordinated with ether linkages, which were found most probable to be labile. Simulated stress–strain data indicates that increasing the water content deteriorates the mechanical properties. The Young’s modulus decreased by ~ 30% when the water content increased to 3 wt%. We conclude, this integration of molecular-level chemical insights with mechanical property simulations of the hydrated epoxy system and experimental validation holds the promise to advance lightweight joint technologies.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability

In contrast to freeze-cast ceramics and polymers, few freeze-cast metals have been described, to date. This systematic study on structure-processing correlations in freeze-cast Ti-6Al-4V scaffolds reports how processing parameters determine the architecture formed during the directional solidification of water-based metal slurries and after sintering. Additionally, sedimentation in the slurry during freezing and volume shrinkage during burnout and sintering were found to significantly affect both structure and properties of the scaffolds. In using two freezing rates, 1 and 10 °C min -1 , two water-based polymer solutions as binders (chitosan and carboxymethyl cellulose) and two different metal volume fractions in the slurry, 20 and 30 vol%, Ti-6Al-4V scaffolds could be prepared with pore length, width, and porosity ranging from 41 to 523 μm, 14.5–76.5 μm, and 65 to 34%, respectively. Their compressive strength, stiffness, and toughness (work to 20% strain) fall in the range of 83–412 MPa, 7–29 GPa, and 14–122 MJ m -3 , respectively. In order to improve the properties a select composition was infiltrated with poly(methyl methacrylate). This increased the average yield strength by a factor of 2.3 from 83 to 193 MPa and the average toughness (work to 50% strain) by a factor of 2.7 from 28.1 to 76.8 MJ m -3 .

36 MATERIALS SCIENCE↗

DOE OSTI2025

Curiosity driven exploration to optimize structure–property learning in microscopy

Rapidly determining structure–property correlations in materials is an important challenge in better understanding fundamental mechanisms and greatly assists in materials design. In microscopy, imaging data provides a direct measurement of the local structure, while spectroscopic measurements provide relevant functional property information. Deep kernel active learning approaches have been utilized to rapidly map local structure to functional properties in microscopy experiments, but are computationally expensive for multi-dimensional and correlated output spaces. Here, we present an alternative lightweight curiosity algorithm which actively samples regions with unexplored structure–property relations, utilizing a deep-learning based surrogate model for error prediction. We show that the algorithm outperforms random sampling for predicting properties from structures, and provides a convenient tool for efficient mapping of structure–property relationships in materials science.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Lightweight Metal Stamping Optimization Enabled by Artificial Intelligence

Successfully manufacturing an automotive body structure made via the sheet metal stamping process depends upon simultaneous consideration of component design, tooling design, stamping process control, and material properties. In many cases, introducing lightweight sheet materials (e.g., aluminum alloys, magnesium alloys, advanced high strength steels) holds the potential to significantly reduce vehicle weight, but challenges the stamping process by introducing materials with inherently less ductility. Successful and repeatable applications require co-developing the stamping process controls with the varying material properties, including formability. During the stamping process, as soon as the forming limit of the sheet is exceeded, the material shows localized necking which quickly leads to splits. Controlling process variability to avoid these material splits will enable deployment of less formable, lighter, and stronger materials for stamped automotive components. A typical optimization procedure for manufacturing requires an iterative process involving parameter setting, execution of computational simulations, and modifying the parameters. The entire process demands substantial computational time, making it impractical for real-time feedback towards rapid corrective actions required for in-line control for running production processes. To overcome this challenge, artificial intelligence (AI) can be leveraged to determine optimal manufacturing parameters within a single manufacturing cycle time. This research proposes an in-line optimization framework incorporating a trained AI model to predict kidney-shaped die forming. Preliminary results indicate that the AI framework can accurately predict draw-in values based on a given parameter set, a process referred to as forward prediction. Furthermore, the AI framework can also predict the optimal parameter set that leads to the desired draw-in values, referred to as inverse optimization (or backward prediction). This research has been performed in collaborations with USCAR (US Council for Automotive Research) and AutoForm. The members of USCAR are Ford, GM, and Stellantis.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Turning Natural Herbaceous Fibers into Advanced Materials for Sustainability

Considering the growing concerns about natural resource depletion, energy inequality, and climate crises, biomass-derived materials—the most abundant organic matter on the planet—have received a lot of attention as a potential alternative to petroleum-based plastics. Herbaceous biomasses and extracted cellulose have recently been extensively used in the development of high-performance and multifunctional materials. Herbaceous biomass has sparked interest due to its species diversity, abundance, low cost, lightweight, and sustainability. This review discusses the structure versus property relationships of various sources of herbaceous biomasses (e.g., sugarcane, straw, and bamboo) and their extracted biomaterials, as well as the latest emerging applications from macro- and microscales to nanoscales. We report, high-strength structural materials, porous carbon materials, multichannel materials, and flexible materials are examples of these applications, which include sustainable electronics, environmentally friendly energy harvesting, smart materials, and biodegradable structural buildings.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Reviewing computational studies of defect formation and behaviors in carbon fiber structural units

Solid-state carbon materials, such as graphite and graphene, are at the forefront of materials research because of their unique electronic, vibrational, and mechanical properties, leading to a broad range of potential and realized applications. One key application is their role as basic structural units of carbon fiber (CF), a lightweight alternative to steel. In CF, a delicate relationship exists between ultimate material strength and the atomic-scale density of defects contained at the inter- and intra-subunit levels. Computational studies provide insight into the stability of various types of defects that can form in these systems and connect with experimental observables such as bandgap and spectroscopic measurements. Therefore, the literature contains many computational studies that focus on changes induced by defects, including vacancies and Dienes transformations (Stone-Wales and Thrower defects). However, wide-ranging methods and cell sizes have been used, and property-specific information is often lacking. Furthermore, this review summarizes key literature findings, paying particular attention to changes in the electronic, vibrational, and mechanical properties induced by defects in graphitic materials relevant to CF.

36 MATERIALS SCIENCE↗